1. Field of the Invention
The present invention relates to an operation of a memory device, and more particularly, to a method for programming a cell in a memory (array) and a memory apparatus utilizing the same.
2. Description of Related Art
A non-volatile memory is characterized by allowing multiple and repetitive writing, reading and erasing operations as well as retaining storage data even after power supply is cut off. The non-volatile memory has become a mandatory component in many electronic products for ensuring normal operation during booting the electronic products, and therefore has been broadly adopted in personal computers (PCs) and other electronic equipments.
In general, a conventional non-volatile memory device is designed to have a stacked gate structure including a floating gate and a control gate both made of doped polysilicon. The floating gate is disposed between the control gate and a substrate, and in a floating state that is not electrically connected with any circuit. The control gate is electrically connected with a word line. In addition, a tunneling oxide layer is disposed between the substrate and the floating gate, while an inter-gate dielectric layer is disposed between the floating gate and the control gate.
Another conventional non-volatile memory is a nitride read only memory which stores data through charge trapping. A charge-trapping structure composed of oxide layer-nitride layer-oxide layer, i.e. a well-known ONO layer, is capable of storing 2-bit data. In general, 2-bit data can be stored respectively at a left side (i.e. a left bit) and at a right side (i.e. a right bit) of the nitride layer in the charge-trapping structure.
Along with the current trend in continuous promotion of device integrity, dimensions of the device are reduced in accordance with the design rule. As the dimensions of the memory device and the memory cells thereof are miniaturized, it is unavoidable that punch-through current between the cells would be more significant. The punch-through current provided by an unselected cell makes a great impact on stability during the programming operation of a selected cell, thereby significantly degrading performance of the memory cells.